Present day semiconductor devices are typically produced from a thin wafer of single crystal semiconductor material (e.g., silicon). In order to produce semiconductor devices, each wafer must undergo a series of process steps which are usually carried out on different processing machines located in separate areas of a manufacturing plant. In many manufacturing facilities, wafers are transported between the machines in a wafer-carrying cassette which has a plurality of spaced pockets each sized to receive an individual wafer. Typically, each cassette carries a batch of 25 wafers. Once the cassette arrives at a machine, it is usually necessary to remove individual wafers from the cassette for processing. Rather than rely on a human operator to accomplish this task, most semiconductor processing machines now produced are provided with an automated wafer load and unload system.
Most wafer load and unload systems employ two separate mechanisms in order to remove a wafer from a cassette and transport it to a processing station on the machine. The first of the two mechanisms usually takes the form of a spatula which adapted for insertion into, and withdrawal from, a selected pocket in the cassette to remove or insert a wafer. The second mechanism typically takes the form of a movable vacuum pickup device which serves to transport the wafer between the spatula and the processing station.
The need for two separate mechanisms in order to transport wafers between the cassette and the processing station on the machine makes present day wafer load and unload systems mechanically complex and inefficient. As a result, such systems tend to be relatively slow and expensive. Therefore, there is a need for a simple technique for transporting a semiconductor wafer.